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Radon Potential Map
Explanation Area radon potentials are from a
computerized spatial analysis of bedrock geology, surficial materials,
and
surface radioactivity mapping, with indoor air and bedrock well water
data. The radon data includes 4721
homes and 958 bedrock wells tested for radon statewide between the years
1985 - 1995. The testing was
conducted by the CT Department of Environmental Protection, CT
Department of Public Health, U.S. Geological
Survey, University of Connecticut and the Stamford Department of Health.
Radon measurements have been correlated with geological and geophysical
factors enabling the mapping
potential. Digital resource maps were scored separately for radon
potential, and compared to indoor air
analyses to determined the usefulness of each resource map for the
prediction of radon. The radon potential
map is a summation of radon scores developed from these earlier
analyses.
Surface radioactivity measurements provide summary information for total
gamma emissions from all areas of
the state. There is a direct correlation between surface radioactivity
and average indoor radon. Area with
the highest surface radioactivity correlate with areas of highest
average indoor radon and are therefore
scored with the highest radon potential.
Surfical materials units are used as a measure of surface permeability
and potential radon transport to the
surface. As such, surficial material units are assigned radon scores
according to their texture. Areas of
coarse-grained sediments are assigned higher radon source than areas of
fine-grained sediments. Each
bedrock unit is assigned a radon score based on the average radon in
well water of that unit, or by
reference to similar geologic units.
The scoring strategies have been tested by comparing radon scores for
each component resource map with
indoor air radon data. Each of these scoring strategies provide a
positive correlation between average
indoor air and the assigned radon scores of individual mapping
components. The areas of more permeable
sediments, higher bedrock well water radon, and higher surface
radioactivity have higher average indoor
radon.
Scores for Component Resource Maps
| Radon Potential
Score |
5 |
4 |
3 |
2 |
1 |
| Surface
Radiation
(counts per second gamma) |
> 900 cps |
900-700 cps |
700-500 cps |
500-300 cps |
<300 cps |
| Surficial
Materials |
---------- |
gravel &
coarse sand |
mixed sands |
mixed fines |
fines & clays |
| Bedrock Well
Water |
> 10,000 pCi/L |
9,999-5,000 pCi/L |
4,999-3000 pCi/L |
2,999-300 pCi/L |
<300 pCi/L |
The combined scores of component resource maps create a total radon
potential score for each area of the
state. These scores range from totals of 4 to 13. Frequency analyses
show a progressive increase in average
indoor radon with total radon potential score.
The total scores are grouped into 4 categories by similar average indoor
radon. These categories are shown
on the map as radon potential ratings. These radon potential ratings
describe areas of statistically
different indoor radon levels.
Sites of naturally occurring radioactive minerals referenced in the
geologic literature are approximately
located on this map where possible. These sites include an assemblage of
various minerals which may produce
locally high radon. These sites are included on the map for reference
and are not part of the development
of the radon potential ratings.
These mineral locations may be useful tools in the development of
regional and local level radon potential
evaluations.
Source: Connecticut Department of Public Health <Top>
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